For full-color display devices, a liquid crystal display (LCD), a plasma display panel (PDP), and an electroluminescent display (ELD) are commonly known. The LCD is a reactive-type (non-luminescent-type) display and has a display region consists of many pixels. Each pixel is divided into a red (R) region, a green (G) region, and a blue (B) region. The R, G, and B regions have a red filter, a green filter, and a blue filter, respectively. RGB components in a white light emitted from the backlight unit are selectively passed to a front surface of the LCD. In the LCD, a full-color image is displayed by adjusting a balance of the RGB components. The balance is adjusted by controlling a voltage applied to a liquid crystal cell corresponding to each region of each pixel.
The PDP is an emissive-type display that includes a discharge cell for each RGB region of each pixel. For example, the discharge cell arranged corresponding to a red region emits a red light when red phosphors are exposed to ultraviolet rays produced by a discharge and excited. RGB components of light are balanced by controlling the intensity of the discharge cell corresponding to each RGB region for full-color display.
A full-color display device displays meters, warning signs, and navigation information is proposed in JP-A-11-91461. In this device, the warning signs are displayed in red or orange. However, the visibility of the warning sings is not good if they are lit in one of or close to the three primary colors, such as red or orange. This is because two other colors in each pixel used for warning display are blocked by the LCD layer and the intensity is reduced to one third of white luminance. In the case of the PDP and ELD, the light emission of the two colors is reduced and the intensity is also reduced to one third of white luminance.